An aircraft may be equipped with high-lift devices, such as slats on a fixed leading edge of a wing and flaps on a fixed trailing edge of the wing. The high-lift devices are typically deployed during take-off and/or landing phases of a flight in order to increase the lift coefficient of the wing during relatively low speed flight. The slats and flaps are mounted from the wing for movement between a retracted and one or more extended (deployed) positions.
A slat deployment mechanism for supporting and controlling the slat generally comprises two or more support tracks driven by rollers mounted within the wing. The slat tracks are typically coupled to the slat by a so called “knuckle”, and each slat track/knuckle is accommodated by an aperture in the fixed leading edge panels (upper “D nose” panel and lower cover panel). The slat tracks are operable to move the slat between the retracted and the one or more extended positions.
A closing plate is typically mounted to the underside of the slat track immediately behind the knuckle, such that on retraction of the slat the plate closes a gap between a lower trailing edge of the slat and a lower edge of the aperture in the fixed leading edge.
In some legacy aircraft wing designs, such as described in GB2204538A, the closing plate is a rigid metallic plate. However, a relatively large clearance gap is required around the closing plate to avoid contact with the surrounding structure, which reduces aerodynamic efficiency.
More recently, it has been proposed to arrange the closing plate such that a periphery of the plate overlaps an area of the surrounding structure (the outer surfaces of the slat and the fixed leading edge) when the slat is retracted. The overlap provides some improvement in aerodynamic efficiency. Setting the closing plate to the desired offset to avoid contact with the surrounding structure, so as to avoid fretting, can be time consuming. This can be particularly problematic if the closing plate overlaps with an access panel as the closing plate may need to be removed and accurately re-set each time the access panel is removed and replaced. Alternatively, the overlapping closing plate can be moved out of the way of the access panel by deploying the slat, but this entails procedures to ensure the slats are not retracted whilst the maintenance is underway.